Phase II Study of Olaparib and Pembrolizumab in Advanced Melanoma With Homologous Recombination (HR) Mutation

Inclusion Criteria:

* Histologically confirmed diagnosis of unresectable or metastatic stage III or IV melanoma
* Must have genetic HR mutation/ alteration including ARID1A/B, ARID2, ATM, ATR, BARD1, BRCA1/2, BAP1, BRIP1, CHEK2, FANCA, FANCD2, MRN11A, PALB2, RAD50, RAD51, RAD54B
* Disease must be refractory or resistant to anti PD-1 therapy (defined as disease progression within 6 months after the last dose of anti PD-1 antibody therapy) and, for V600 BRAF mutation, disease must be progressed after BRAF inhibitor therapy; or patients could not have tolerated the standard therapies.
* Must have measurable disease based on RECIST 1.1.
* Must have an ECOG performance status of 0 to 1.
* Prior systemic cytotoxic therapy up to 1 regimens is allowed; There is no limit on the number of prior immunotherapy or targeted therapy regimens.
* Must have recovered from all AEs due to previous therapies to ≤Grade 1 or baseline.

Exclusion Criteria:

* Previously treated with a PARP inhibitor
* Has received prior radiotherapy within 2 weeks of start of study treatment. A 1-week washout is permitted for palliative radiation (≤2 weeks of radiotherapy) to non-CNS disease.
* Has a diagnosis of immunodeficiency or is receiving chronic systemic steroid therapy (in dosing exceeding 10 mg daily of prednisone equivalent) or any other form of immunosuppressive therapy within 7 days prior to the first dose of study drug.
* Has a known additional malignancy that is progressing or has required active treatment within the past 2 years
* Previous solid organ or allogenic bone marrow transplant or double umbilical cord blood transplantation (dUCBT) for solid tumors.
* Has known active CNS metastases and/or carcinomatous meningitis. Participants with previously treated brain metastases may participate provided they are radiologically stable, i.e. without evidence of progression for at least 4 weeks by repeat imaging (note that the repeat imaging should be performed during study screening), clinically stable and without requirement of steroid treatment for at least 14 days prior to first dose of study treatment.
* Has active autoimmune disease that has required systemic treatment in the past 2 years
* Has a history of (non-infectious) pneumonitis due to a single agent PD-1 / PD-L1 antibody therapy that required steroids or has current pneumonitis.